Electrophysiologically "complex" glial cells freshly isolated from the hippocampus are immunopositive for the chondroitin sulfate proteoglycan NG2

J Neurosci Res. 2003 Sep 15;73(6):765-77. doi: 10.1002/jnr.10680.


We have recently described a subgroup of isolated glial fibrillary acidic protein-positive (GFAP+) hippocampal astrocytes that predominantly express outwardly rectifying currents (which we term "ORAs" for outwardly rectifying astrocytes), which are similar to the currents already described for hippocampal GFAP- "complex glia." We now report that post-recording staining of cells that were first selected as "complex" by morphology and then confirmed by their electrophysiological characteristics were NG2+ approximately 90% of the time. Also, the morphology of freshly isolated NG2+ cells differs from that of isolated GFAP+ ORAs in having a smaller and round cell body with thinner processes, which usually are collapsed back onto the soma. Upon detailed examination, NG2+ cells were found to differ quantitatively in some electrophysiological characteristics from GFAP+ ORAs. The outward, transient K+ currents (IKa) in the NG2+ cells showed a slower decay than the IKa in ORAs, and their density decreased in NG2+ cells from older animals. The other two major cation currents, the voltage-activated Na+ and outwardly delayed rectifier K+ currents, were similar in NG2+ cells and ORAs. To further distinguish isolated complex cells from outwardly rectifying GFAP+ astrocytes, we performed immunocytochemistry for glial markers in fixed, freshly isolated rat hippocampal glia. NG2+ cells were negative for GFAP and also for the astrocytic glutamate transporters GLT-1 and GLAST. Thus the isolated hippocampal NG2+ glial cells, though having an electrophysiological phenotype similar to that of ORAs, are an immunologically and morphologically distinct glial cell population and most likely represent NG2+ cells in situ.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Transport System X-AG / metabolism
  • Anesthetics, Local / pharmacology
  • Animals
  • Animals, Newborn
  • Antigens / analysis*
  • Antigens / immunology
  • Cell Count
  • Cells, Cultured
  • Electric Conductivity
  • Glial Fibrillary Acidic Protein / immunology
  • Hippocampus / cytology*
  • Hippocampus / metabolism
  • Immunohistochemistry / methods
  • Neuroglia / classification
  • Neuroglia / drug effects
  • Neuroglia / metabolism*
  • Neuroglia / physiology
  • Patch-Clamp Techniques / methods*
  • Proteoglycans / analysis*
  • Proteoglycans / immunology
  • Rats
  • Tetrodotoxin / pharmacology
  • Time Factors


  • Amino Acid Transport System X-AG
  • Anesthetics, Local
  • Antigens
  • Glial Fibrillary Acidic Protein
  • Proteoglycans
  • chondroitin sulfate proteoglycan 4
  • Tetrodotoxin